A carbon nanotube is a carbon material which is recently attracting attention. Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2001-220674 discloses an aligned carbon nanotube assembly in which chemical vapor deposition (CVD) processing is applied to a substrate in such a state that a temperature of the substrate is kept at 675 to 750° C., whereby a large number of carbon nanotubes are grown on a surface of the substrate to be substantially vertical to the substrate while being arranged in parallel.
Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2007-76925 discloses an aligned carbon nanotube assembly having a carbon nanotube group, constituted of a large number of carbon nanotubes formed by being implanted on a surface of a substrate, and a metal film interconnecting the roots on the substrate side of the nanotubes of the carbon nanotube group. According to the aligned carbon nanotube assembly, the metal film having a melting point higher than a growth temperature of the carbon nanotube is formed, and a catalyst is provided on the metal film. In this state, the carbon nanotubes are grown on the substrate surface by a raw material gas, and metal is then melted at a temperature higher than the growth temperature of the carbon nanotube and thereafter solidified, whereby the root portions of the carbon nanotubes are covered and fixed with the metal. Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2008-120658 discloses an aggregative structure of multiwall carbon nanotubes in which a large number of carbon nanotubes are aggregated in ultrahigh density on a surface of a silicon substrate while vertical alignment is maintained with respect to the surface of the silicon substrate.
Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2007-182352 discloses a technique for manufacturing an aligned carbon nanotube assembly. In this technique, an assembly of grown carbon nanotubes is subjected to a compression process in which the aligned carbon nanotube assembly is exposed to a liquid such as water as compaction secondary processing to be thereafter dried and, thus, to be compressed, whereby the assembly of the carbon nanotubes is densified. This patent literature describes that the aligned carbon nanotube assembly can be densified by being subjected to the compaction secondary processing after the growth of the carbon nanotubes. Further, Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2007-182352 discloses a technique of applying a compression processing as the compaction secondary processing, in which compression is performed by application of a mechanical external pressure, to an aligned carbon nanotube assembly, thereby densifying the aligned carbon nanotube assembly.
Further, Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2003-205499 discloses a technique in which a carbon nanostructure is formed, then, as post-treatment, ultrasonic waves are applied to the carbon nanostructure for approximately 3 to 6 hours in such a state that the carbon nanostructure is dispersed in a solvent in a liquid form, whereby defective pores are actively formed as defects in a six-membered carbon ring array structure (graphene sheet) as a graphite layer of the carbon nanostructure. This document describes that the graphite layer of the carbon nanostructure can be effectively modified by addition of other components.